I was looking for a road atlas in the boot of my wife's car when I found a bag containing a set of black underwear – a basque, stockings, a suspender belt and thong panties. This surprised me as my wife usually wears very practical underwear, not these sexy items. I also noticed that the car was quite muddy and the seats seemed to have faint stains on them as did the windows. She only really uses her car to run into town and to go to her yoga classes on a Friday night. – not places where the car would get muddy. I thought of asking her about these things but assumed that she would lie if she had anything to hide. My suspicion was that perhaps she was seeing someone else. We are in our 40s and our sex life is fairly mundane with a mutual lack of interest. However, I found that I was becoming aroused at the thought of my wife seeing another man. This was not too much of a surprise to me as I had always enjoyed pornography with the theme of wives having sex with other men. I decided to follow her on the next Friday night and borrowed a neighbour’s car to do so, and sure enough instead of going to the yoga class she went to a house nearby, took the bag containing the underwear out of the boot, and rang the bell on the house. The door was opened by a good looking man in his early 30’s. I crept around the back of the house and hid in the bushes where I could see through the patio doors of the house. I could just make out my wife quickly undressing and putting on the black underwear. While she was doing this the man was running his hands over her body but she seemed impatient of this and was fending him off. However, the sight of my normally frumpy wife in stockings and suspenders with a man fondling her breasts was incredibly exciting for me and my cock was ramrod hard as I watched. As soon as she had finished dressing she put her coat on and they made for her car and drove off. I followed at a distance and after driving out of town for a couple of miles they pulled into a local beauty spot. It was fairly dark by now but there were quite a few cars in the car park there; they parked at one end of the area, I parked at the other. It was dark enough for me to get out of the car without them seeing who I was and, as I walked towards their car, I noticed that there were small groups of men standing around one or two of the cars which had their interior lights on. I approached the nearest one and to my surprise saw a couple fucking in the car with three men watching through the windows. As I peered in it was obvious that the couple had just finished and the show was over; but one of the three men pointed to my wife’s car and said that the woman there was a real slut and would sometimes let the watchers join in. My heart was in my mouth and my cock uncomfortable in my trousers as we approached my wife’s car. There were already two other men there and they had their cocks out and were wanking. When I looked through the back window I could see my wife spread out on the back seat in just her stockings and suspenders with her boyfriend pumping his large cock in and out of her cunt. My cock became rock hard and I released it from my trousers and joined the other three in wanking while we watched. Suddenly the rear side windows came down and my wife grabbed the nearest cock while one of the other men began to maul her breasts. The third man pushed his cock through the window and she began sucking it as her lover came with a grunt as he pumped his cum into her cunt. The cock in her mouth erupted, the cum running out of the corners of her mouth. The cock she was wanking shot its load over her face and hair. The cum from cock splattered over the rear window. I quickly zipped myself up and returned to my car and drove home. I was in bed when my wife returned. She showered and came to bed in her frumpy nightie and gave me a peck on the cheek. I asked how her yoga was – “we tried some interesting positions tonight” she said.